API-571 Exam Dumps

API RP 571, Naphthenic Acid Corrosion:

''Molybdenum significantly improves resistance to naphthenic acid attack. Alloys such as 317, 316Mo, and Alloy 20 are used in severe NAC environments due to higher Mo content.''

''Chromium and nickel play secondary roles; molybdenum is the key element.''

Answer is A -- Molybdenum.

Comprehensive and Detailed Explanation From Exact Extract:

Per API RP 571, mechanical fatigue failures are identified by the presence of beach marks or clam shell patterns on the fracture surface.

These features:

Appear as concentric rings

Represent successive crack growth increments

Radiate outward from the crack initiation site

This ''clam shell'' or ''beach mark'' appearance is one of the most recognizable signatures of fatigue failure.

Referenced Documents (Study Basis):

API RP 571 -- Section on Mechanical Fatigue

Comprehensive and Detailed Explanation From Exact Extract:

Hydrochloric acid (HCl) corrosion, particularly in crude unit overhead systems, is aggressive toward carbon steel and stainless steels.

According to API RP 571, nickel-based alloys, such as Monel (Ni--Cu alloys), exhibit excellent resistance to hydrochloric acid corrosion and are commonly used for:

Overhead piping

Injection quills

High-risk corrosion zones

Why the other options are incorrect:

Duplex and 300 series stainless steels are highly susceptible to chloride corrosion and SCC.

Copper-based materials alone lack sufficient resistance and structural strength in refinery HCl environments.

Referenced Documents (Study Basis):

API RP 571 -- Section on Hydrochloric Acid Corrosion

API RP 571 states under Galvanic Corrosion:

''Because galvanic corrosion usually manifests as thinning of the more anodic metal, ultrasonic thickness measurements taken near dissimilar metal joints are an effective way to detect this type of internal corrosion.''

''Surface NDE techniques like liquid penetrant or magnetic particle testing are not effective for detecting wall loss.''

Thus, option D (ultrasonic thickness testing) is correct.

From API RP 571, under Cooling Water Corrosion:

''If proper water treatment is not feasible or consistently maintained, upgrading the metallurgy of exchanger tubes to more corrosion-resistant materials such as stainless steel or titanium may be necessary.''

''This is especially important in seawater or brackish water cooling applications or in once-through systems.''

(Reference: API RP 571, Section 4.3.1.1 -- Cooling Water Corrosion)

Thus, the most effective long-term solution in cases of uncontrolled water quality is to upgrade metallurgy, making option C correct.